Search found 60 matches

by David Liu 1E
Mon Jan 18, 2021 12:58 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units to know
Replies: 8
Views: 16

Re: Units to know

we mainly need to know atm and torr!
by David Liu 1E
Mon Jan 18, 2021 12:56 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 1 #5
Replies: 8
Views: 38

Re: Sapling Week 1 #5

you multiply them to add them together!
by David Liu 1E
Mon Jan 18, 2021 12:56 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Week 1 Sapling 10
Replies: 6
Views: 22

Re: Week 1 Sapling 10

sapling gives everyone different values, but we're graded on completion so you should always try your answer if you think you solved it!
by David Liu 1E
Mon Jan 18, 2021 12:51 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: quadratic formula values
Replies: 8
Views: 31

Re: quadratic formula values

even though both are positive, only one should make sense given the conditions of the question
by David Liu 1E
Mon Jan 18, 2021 12:49 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: equilibrium shifts: left of right?
Replies: 9
Views: 17

Re: equilibrium shifts: left of right?

it would shift right because according to the equilibrium there would now be too much reactant and it shifts to the products in order to achieve equilibrium again
by David Liu 1E
Sun Jan 10, 2021 11:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: change in K
Replies: 22
Views: 62

Re: change in K

k is only affected by temperature!
by David Liu 1E
Sun Jan 10, 2021 11:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling HW 1 #5
Replies: 8
Views: 51

Re: Sapling HW 1 #5

make sure to factor/remember to use inverse reactions for these types of questions! It was something I forgot about when I first did it too
by David Liu 1E
Sun Jan 10, 2021 10:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K Favors Products or Reactants
Replies: 20
Views: 67

Re: K Favors Products or Reactants

A large k value is anything over 10^3 and a small value would be anything lower than 10^-3!
by David Liu 1E
Sun Jan 10, 2021 10:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units
Replies: 27
Views: 80

Re: Units

should be bars and atm for units that we've seen so far!
by David Liu 1E
Sun Jan 10, 2021 10:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration vs Pressure
Replies: 9
Views: 25

Re: Concentration vs Pressure

for the questions that we've discussed, I think that they mean the same thing for calculations (though it'll get harder and we'd need to know the difference later)
by David Liu 1E
Wed Dec 16, 2020 2:16 pm
Forum: Lewis Acids & Bases
Topic: Acids & Bases
Replies: 9
Views: 72

Re: Acids & Bases

you should look at what accepts/loses an electron/proton and that will tell you which ones act as an acid or base! You could also memorize certain patterns like how anything that starts with h is generally an acid and anything ending with oh is usually a base (and the group 1 and group 2 patterns)
by David Liu 1E
Wed Dec 16, 2020 2:15 pm
Forum: Lewis Acids & Bases
Topic: Ligands
Replies: 6
Views: 52

Re: Ligands

a ligand is just a lewis base (donates electrons) to a metal usually to form a coordinate compound
by David Liu 1E
Wed Dec 16, 2020 2:13 pm
Forum: Lewis Acids & Bases
Topic: Lewis vs Bronsted
Replies: 20
Views: 85

Re: Lewis vs Bronsted

lewis acids/bases focus on electrons, while bronsted focuses on the transfer of h+ ions
by David Liu 1E
Wed Dec 16, 2020 2:12 pm
Forum: Einstein Equation
Topic: units for E=hv
Replies: 11
Views: 111

Re: units for E=hv

I think it's normally j/photon, but you would check with the question to make sure because sometimes it can change to j/atom
by David Liu 1E
Wed Dec 16, 2020 2:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: paired and parallel
Replies: 10
Views: 55

Re: paired and parallel

paired electrons and parallel spin are different! paired electrons are the 2 that would be in the ml orbital with opposite spins (-1/2 and 1/2) and parallel electrons are ones that have the same spin meaning they're definitely not paired
by David Liu 1E
Mon Dec 07, 2020 4:11 pm
Forum: Electronegativity
Topic: Acidity
Replies: 4
Views: 16

Re: Acidity

the more electronegative an atom is the stronger acid it'll be generally
by David Liu 1E
Mon Dec 07, 2020 4:00 pm
Forum: Lewis Acids & Bases
Topic: Acids vs Basis
Replies: 11
Views: 95

Re: Acids vs Basis

I agree with a lot of the responses mentioning that you most likely have to look at the definitions of what you want but a rule of thumb would be to look at the H and OH groups at the ends of the compound
by David Liu 1E
Mon Dec 07, 2020 3:53 pm
Forum: Lewis Acids & Bases
Topic: Water
Replies: 62
Views: 480

Re: Water

it can act as either depending on the question and the other compounds
by David Liu 1E
Mon Dec 07, 2020 3:50 pm
Forum: Lewis Acids & Bases
Topic: sapling #6
Replies: 19
Views: 99

Re: sapling #6

the carboxyl groups shows that it's an acid!
by David Liu 1E
Sun Dec 06, 2020 2:40 am
Forum: Naming
Topic: what does (en) mean?
Replies: 23
Views: 155

Re: what does (en) mean?

do you guys know if we'll need to know this by memory for this class/series? wondering if it's something I should look at before the exam in case it shows up
by David Liu 1E
Sun Dec 06, 2020 2:38 am
Forum: Ionic & Covalent Bonds
Topic: lone pairs -polar molecule
Replies: 10
Views: 92

Re: lone pairs -polar molecule

I would definitely first look at the bond angles, because not every molecule with lone pairs would be polar as they could be evenly spaced from each other
by David Liu 1E
Sun Dec 06, 2020 2:36 am
Forum: Properties of Light
Topic: Is c always the speed of light?
Replies: 88
Views: 456

Re: Is c always the speed of light?

for this class c is always the constant value for speed of light!
by David Liu 1E
Sun Dec 06, 2020 2:34 am
Forum: Significant Figures
Topic: When should I start looking at sig figs?
Replies: 31
Views: 231

Re: When should I start looking at sig figs?

My ta mentioned that you would get the best answer by being as exact during calculations and rounding at the end only for the best/safest results
by David Liu 1E
Sat Dec 05, 2020 7:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.13 Part D, Determining the bond angle of N2O
Replies: 5
Views: 46

Re: 2E.13 Part D, Determining the bond angle of N2O

definitely should be 180! I checked my textbook and it says 180 if that helps
by David Liu 1E
Sat Dec 05, 2020 7:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: difference
Replies: 4
Views: 33

Re: difference

they have different amounts of electron dense areas - trigonal planar has 3 electron dense (paired) areas while t-shaped has 5 electron dense areas while 2 are lone pairs (aka there should be a different amount of electrons on the molecule that will help you tell)
by David Liu 1E
Mon Nov 23, 2020 9:49 pm
Forum: Lewis Structures
Topic: Dot stucture
Replies: 11
Views: 66

Re: Dot stucture

You would first count the valence electrons and then create the dot structure around it based on bonds that you need to create and lone pairs
by David Liu 1E
Mon Nov 23, 2020 9:46 pm
Forum: Lewis Structures
Topic: Week 8 Sapling Homework #13
Replies: 3
Views: 21

Re: Week 8 Sapling Homework #13

I would just focus on each one individually, as the structures of each tend to be self-explanatory. If the overall structure affects it, I would focus on that after looking at each individual carbon
by David Liu 1E
Mon Nov 23, 2020 9:35 pm
Forum: Lewis Structures
Topic: Lewis acids and Bases
Replies: 20
Views: 119

Re: Lewis acids and Bases

lewis acids are compounds/elements that accept electrons, and bases will donate electrons. acids and bases donate/accept in lone pairs, so it's a matter of seeing which ones can donate a lone pair or give one up.
by David Liu 1E
Mon Nov 23, 2020 9:30 pm
Forum: Lewis Structures
Topic: Octet Rule
Replies: 17
Views: 133

Re: Octet Rule

like lavelle said in lecture, I feel like it's important to note that the "normal" elements we use generally follow the trend, but any element that has access to the d orbital past period 3 can generally overcome the octet rule
by David Liu 1E
Mon Nov 23, 2020 9:18 pm
Forum: Properties of Electrons
Topic: intensity vs energy
Replies: 29
Views: 239

Re: intensity vs energy

it should be false because intensity is based on how many photons there are, while energy is focused on the individual photon!
by David Liu 1E
Sun Nov 15, 2020 8:27 pm
Forum: Ionic & Covalent Bonds
Topic: Homework due date
Replies: 49
Views: 336

Re: Homework due date

the homework is due tonight! it's always the same time as chem community too~ :)
by David Liu 1E
Sun Nov 15, 2020 8:26 pm
Forum: Dipole Moments
Topic: hydrogen bonding and ice
Replies: 4
Views: 8

Re: hydrogen bonding and ice

with ice it forms a lattice structure that actually makes the structure have less density, because water is more dense in liquid form as it flows freely and forms/reforms bonds while in ice all the molecules are structured
by David Liu 1E
Sun Nov 15, 2020 8:23 pm
Forum: Dipole Moments
Topic: Sapling #13
Replies: 9
Views: 52

Re: Sapling #13

you locate the amount of N,O,and F atoms that a hydrogen bond can form, and then you check how many lone pairs each one of these have for a hydrogen bond to form with!
by David Liu 1E
Sun Nov 15, 2020 8:20 pm
Forum: Dipole Moments
Topic: H-Bond acceptor
Replies: 9
Views: 70

Re: H-Bond acceptor

it doesn't need to be attached to a hydrogen, but you need ot make sure there's a partial charge on the molecule that it's attached to, which is why in the sapling homework it generally can't attach to a carbon that has 4 bonds (because it becomes nonpolar)
by David Liu 1E
Sun Nov 15, 2020 8:13 pm
Forum: Dipole Moments
Topic: Sapling W 5/6 #17
Replies: 10
Views: 108

Re: Sapling W 5/6 #17

I think it's really helpful to draw out the structure because LD forces can only be used with nonpolar molecules, so drawing out the structures generally gives you an idea of how they should work, besides a few exceptions
by David Liu 1E
Mon Nov 09, 2020 2:01 am
Forum: Student Social/Study Group
Topic: Midterm 2 Study Group
Replies: 25
Views: 146

Re: Midterm 2 Study Group

thank you for organizing this! hope we all do well :')
by David Liu 1E
Mon Nov 09, 2020 1:59 am
Forum: Ionic & Covalent Bonds
Topic: Size of Bonds
Replies: 28
Views: 99

Re: Size of Bonds

double bonds hold electrons together more closely, which is shown as it takes more to break a double bond over a single bond. Because they're more tightly bound, they tend to be smaller
by David Liu 1E
Mon Nov 09, 2020 1:58 am
Forum: Ionic & Covalent Bonds
Topic: Electronegativity
Replies: 16
Views: 90

Re: Electronegativity

flourine only needs one electron, which means that it has a high electronegativity as it doesn't need a lot of electrons to fill it's outer shell
by David Liu 1E
Mon Nov 09, 2020 1:57 am
Forum: Ionic & Covalent Bonds
Topic: Sulfate
Replies: 8
Views: 28

Re: Sulfate

sulfate/sulfur can have expanded d- orbitals; I'm not entirely sure why it happens, but because it has something to do with the d-orbitals elements in the second period can't have expanded octets, which is why sulfur is an example
by David Liu 1E
Mon Nov 09, 2020 1:54 am
Forum: Ionic & Covalent Bonds
Topic: Difference Between Ionic & Covalent Bonds
Replies: 11
Views: 63

Re: Difference Between Ionic & Covalent Bonds

covalent bonds generally share electrons in a pair, while ionic bonds generally result in ionization where one atom donates electrons to another
by David Liu 1E
Sun Nov 01, 2020 9:21 pm
Forum: Ionic & Covalent Bonds
Topic: Sampling 28
Replies: 10
Views: 54

Re: Sampling 28

the max l value is always one less than the n value, and you can tell what it's in by the orbital that's stated. s=0, p=1, d=2, f=3 and so on
by David Liu 1E
Sun Nov 01, 2020 9:18 pm
Forum: Ionic & Covalent Bonds
Topic: intermolecular vs intramolecular
Replies: 17
Views: 297

Re: intermolecular vs intramolecular

Do we need to know how to identify intramolecular forces? I'm pretty sure there are only 3 intramolecular forces (ionic, covalent, and metallic bonding) and it's not too hard to remember so I would just make sure to know the difference between the two. Intramolecular forces are bonds because it all...
by David Liu 1E
Sun Nov 01, 2020 9:15 pm
Forum: Electronegativity
Topic: Electronegativity
Replies: 10
Views: 169

Re: Electronegativity

electronegativity is how much an electron is drawn to an atom, and we can see the trends on a periodic table (as we probably won't have to know specific electronegativity numbers for this class)
by David Liu 1E
Sun Nov 01, 2020 9:13 pm
Forum: Ionic & Covalent Bonds
Topic: hydrogen
Replies: 19
Views: 230

Re: hydrogen

N, O, and F have the strongest attraction to a hydrogen because they are all really close to their octet, and it was mentioned that in most of the time we would see hydrogen primarily bind to these elements
by David Liu 1E
Sun Nov 01, 2020 9:10 pm
Forum: Ionic & Covalent Bonds
Topic: Is ionic or covalent stronger?
Replies: 31
Views: 369

Re: Is ionic or covalent stronger?

I'm pretty sure ionic bonds are stronger for this class, but as comments above have said, it seems that covalent bonds are stronger for chemistry
by David Liu 1E
Sun Oct 25, 2020 7:42 pm
Forum: SI Units, Unit Conversions
Topic: units to know for midterm
Replies: 11
Views: 149

Re: units to know for midterm

does anyone know if we just use the equation sheet from his website, or will he email another sheet out? I remember someone telling me that their TA said Lavelle would email one for us to print for this test specifically
by David Liu 1E
Sun Oct 25, 2020 7:41 pm
Forum: SI Units, Unit Conversions
Topic: Can someone explain Avogrado's #?
Replies: 8
Views: 91

Re: Can someone explain Avogrado's #?

Avogadro's number is just a set number of anything, and we then assign to units to it based on what we're looking at. Essentially it's like the number 10 or 5, and we assign units to this number to represent what it is (i.e. molecules of water, eggs, test questions, etc.)
by David Liu 1E
Sun Oct 25, 2020 7:36 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity and Electronegativity
Replies: 9
Views: 77

Re: Electron Affinity and Electronegativity

Hi this is probably another dumb question but why does electron affinity increase as we go up and to the right? I understand how electronegativity goes up but not affinity
by David Liu 1E
Sun Oct 25, 2020 7:32 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 6
Views: 74

Re: Orbitals

it's always n-1, and I'm sure where in lecture he stated that, but it should only be for the 0 and 1 orbitals, and not the second!
by David Liu 1E
Sun Oct 25, 2020 7:28 pm
Forum: *Shrodinger Equation
Topic: Sapling Number 6
Replies: 3
Views: 29

Re: Sapling Number 6

everything seems right, so you should probably check the parenthesis of your calculator like the last person said! I've found that adding extra parenthesis is always better (better safe than sorry) and just as a trick you only really need the first parenthesis and you don't need to work on closing i...
by David Liu 1E
Sun Oct 18, 2020 3:31 pm
Forum: Properties of Light
Topic: Energy Levels
Replies: 11
Views: 92

Re: Energy Levels

I think that the levels are more of a concept to help us understand electrons, and as previous posts above have stated with the uncertainty principle, electrons probably travel without stopping to levels as they "jump", as an electron is only in one space for a split second. There's probab...
by David Liu 1E
Sun Oct 18, 2020 3:23 pm
Forum: Properties of Electrons
Topic: protons and electrons
Replies: 33
Views: 191

Re: protons and electrons

electrons have negligible mass and are mostly there for the charge/energy, which is when we use them for calculations! Protons and neutrons are around the same mass and are larger than electrons
by David Liu 1E
Sun Oct 18, 2020 3:20 pm
Forum: Properties of Electrons
Topic: Grading System
Replies: 7
Views: 94

Re: Grading System

from people i've talked to the getting a 50% is a c- until like 73% and then it's a normal grading scale
by David Liu 1E
Sun Oct 18, 2020 3:11 pm
Forum: Student Social/Study Group
Topic: How are you studying?
Replies: 203
Views: 1266

Re: How are you studying?

I'm taking notes/outlining the lectures and sample problems bc they're really useful for understanding the concepts first! I've been doing sapling problems for hw after and then reviewing a few textbook questions on subjects I'm struggling in! I think that starting from the lectures and working your...
by David Liu 1E
Sun Oct 18, 2020 2:49 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Reactions Order
Replies: 31
Views: 236

Re: Balancing Chemical Reactions Order

There isn't one way to do it, but I definitely find it easier to first try to balance out a molecule that has only one product with it on the right side because by attempting to balance it, a lot of the times the rest of the numbers will balance each other out through trial and error!
by David Liu 1E
Sat Oct 10, 2020 4:03 pm
Forum: Limiting Reactant Calculations
Topic: Actual yield
Replies: 20
Views: 194

Re: Actual yield

Actual yield should be able to be calculated given certain information from the problem, though the questions that we've done so far mostly have them given. I think that in the future we might get questions that ask us to calculate both given idealized information but I think all the questions this ...
by David Liu 1E
Sat Oct 10, 2020 3:57 pm
Forum: Significant Figures
Topic: How many significant figures are in 7.00 x 10^2?
Replies: 25
Views: 566

Re: How many significant figures are in 7.00 x 10^2?

There would be 3 sig figs on this because it specified 7.00 and all trailing zeros behind a decimal are significant. If the question had written 700 it would probably be one though, so I'm fairly certain it's based on how the question is worded.
by David Liu 1E
Wed Oct 07, 2020 4:20 pm
Forum: Empirical & Molecular Formulas
Topic: Rounding EF to Integers
Replies: 6
Views: 62

Re: Rounding EF to Integers

If you're using molecular mass, you should get the empirical formula already in it's simplest state without decimals after calculating. You'll use whole numbers for the molecular formula too, so I think that even if you were to somehow get decimals it would be easier to work with whole numbers for t...
by David Liu 1E
Wed Oct 07, 2020 4:16 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: precision for molar masses
Replies: 14
Views: 112

Re: precision for molar masses

what I did on the homework problem was round the really close ones like oxygen (15.999) and selenium (78.96), but like ones that don't round as well I keep to one decimal point. I've gotten all the right answers with sig figs according to the textbook, so it's what I've been doing since it works.
by David Liu 1E
Wed Oct 07, 2020 4:09 pm
Forum: Significant Figures
Topic: Clarification on Significant Figures
Replies: 9
Views: 67

Re: Clarification on Significant Figures

The person who posted above is right! And I'm also kind of rusty on sig figs but I'm pretty sure 0.340 has 3 sig figs, because the sig fig rule is that trailing zeroes to the right of the decimal are significant, so it should count?

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